1. Field of the Invention
The present invention relates to a fire suppression system for a cookstove or a range. In particular, the invention relates to an automatic self-contained fire suppression system which may be installed (retrofitted) in an existing hood over a cookstove or range or which may be constructed with its own hood for installation over a cookstove or range. The system is further described with reference to a particular method for its use.
2. The Prior Art
It is well known to place an exhaust hood over a cookstove or range. Such a hood usually contains a fan and in some cases contains fire suppression equipment.
Known fire suppression equipment used in hoods placed over cookstoves or ranges are disclosed in several prior U.S. patents. These prior patents disclose numerous arrangements for automatically extinguishing stove fires.
Early fire suppression systems for use with cook stoves and ranges were mainly concerned with delivering fire retardant onto the cooking surface to stop a fat or grease fire. The early systems did not include means for shutting down the stove and the exhaust fan, or activating an alarm.
U.S. Pat. No. 3,653,443 to Dockery, which is hereby incorporated by reference, discloses an improved fire suppression system which, in addition to releasing fire retardant, sounds an alarm, shuts down the stove and exhausts smoke. One of the disadvantages of the Dockery system is that it is not easily retro-fitted into existing hoods.
U.S. Pat. Nos. 4,773,485 and 4,834,188 to Silverman, which are hereby incorporated by reference, disclose a fire suppression system which is readily retro-fitted to existing stove hoods. Silverman's system is installed within and adjacent to the stove hood. That is, a portion of Silverman's system is fitted within an existing hood and another portion of Silverman's system is located adjacent to the existing hood and the two portions are connected by a series of conduits, wires and pulleys. A clear disadvantage of Silverman's system is that it is not self-contained. Although Silverman suggests that his system is readily retro-fitted to existing hoods, his system requires substantial modification to the existing hood. Holes must be drilled. Pulleys must be mounted to carry wires attached to fusible links. Nozzles attached to conduits must be mounted inside the hood and the conduits must extend through the existing hood to an external supply of fire retardant.
U.S. Pat. Nos. 4,813,487 and 4,979,572 to Mikulec, which are hereby incorporated by reference, disclose a system similar to Silverman's, but which does not require so much drilling and cutting of the existing hood. Mikulec's system provides most of the mechanical parts in a single piece which is mounted from the rear of an existing hood at a specified angle. This piece is also connected by wire to a device for shutting down the stove. One of the disadvantages of Mikulec's system is that there must be room for it behind the existing hood and the angle of mounting is limited. Moreover, Mikulec's system is limited in features, being essentially a fire extinguisher and a stove shut off switch. In addition, Mikulec's system leaves components exposed to direct heat, grease, and possible fire thereby compromising the operation of the system.
U.S. Pat. No. 4,830,116 to Walden et al., which is hereby incorporated by reference, discloses a fire suppression system where tanks containing fire suppression fluids are located remote from the hood. The system includes means for shutting down the stove, sounding an alarm and activating an exhaust fan. Walden's system is clearly not self-contained and is not easily retrofitted to existing hoods.
All of the known systems have particular disadvantages, some of which are mentioned above. No one of the known systems contains all of the features taught by all of the other systems. Also, while, most stove fires are the result of grease or fat, none of the known systems pays particular attention to the danger of splashing the grease or fat when fire retardant is sprayed through a nozzle over the stove. Unless the nozzles are properly positioned, the first spray of fire retardant may serve only to spread the burning fat or grease beyond the stove top. Moreover, cooking fat and grease always accumulates in the hood over the stove and can clog nozzles unless special measures are taken to prevent this. None of the known systems addresses this problem. Further, all of the known systems rely on a pressurized supply of fire retardant, but none of them provide any means for warning when the pressure is too low to be effective in releasing the supply of fire retardant. While two of the known systems (Silverman and Walden) provide a pressure sensing means at the supply of fire retardant, the pressure sensing means is used to sense release of the retardant and shut down the stove. None of the known systems contains a means for warning that the system may not operate properly because the pressure has dropped too low.
Finally, and perhaps most importantly, all of the prior art systems tend to act in only two modes: on or off. In other words, all of the features are activated simultaneously or automatically with a predetermined time delay or not at all. This assumes that all stove fires will require the same treatment and that no early warning or provisional measures can be used to avert a serious fire without engaging the full force of the suppression system. However, it should be appreciated that the release of fire retardant is a drastic step which should be used as a last resort.